Wavelength converted semiconductor light emitting device

ABSTRACT

In some embodiments of the invention, a device includes a semiconductor light emitting device having a first light extraction surface, a wavelength converting element, and a second light extraction surface. A majority of light extracted from the semiconductor light emitting device is extracted from the first light extraction surface. The first light extraction surface has a first area. The second light extraction surface is disposed over the first light extraction surface and has a second area. The first area is larger than the second area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/533,158 filed Jun. 5, 2017 and titled “WAVELENGTH CONVERTEDSEMICONDUCTOR LIGHT EMITTING DEVICE, which was filed as a § 371application of International Application No. PCT/US2015/064527 filed onDec. 8, 2015 and titled “WAVELENGTH CONVERTED SEMICONDUCTOR LIGHTEMITTING DEVICE”, which claims the benefit of U.S. Provisional PatentApplication No. 62/088,834 filed Dec. 8, 2014.

U.S. patent application Ser. No. 15/533,158, International ApplicationNo. PCT/US2015/064527, and U.S. Provisional Patent Application No.62/088,834 are each incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a semiconductor light emitting devicewith increased luminance.

BACKGROUND

Semiconductor light-emitting devices including light emitting diodes(LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavitylaser diodes (VCSELs), and edge emitting lasers are among the mostefficient light sources currently available. Materials systems currentlyof interest in the manufacture of high-brightness light emitting devicescapable of operation across the visible spectrum include Group III-Vsemiconductors, particularly binary, ternary, and quaternary alloys ofgallium, aluminum, indium and nitrogen, also referred to as III-nitridematerials. Typically, III-nitride light emitting devices are fabricatedby epitaxially growing a stack of semiconductor layers of differentcompositions and dopant concentrations on a sapphire, silicon carbide,III-nitride, or other suitable substrate by metal-organic chemical vapordeposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxialtechniques. The stack often includes one or more n-type layers dopedwith, for example, Si, formed over the substrate, one or more lightemitting layers in an active region formed over the n-type layer orlayers, and one or more p-type layers doped with, for example, Mg,formed over the active region. Electrical contacts are formed on the n-and p-type regions.

SUMMARY

It is an object of the invention to provide a wavelength converted lightemitting device with increased luminance.

In some embodiments of the invention, a device includes a light emittingdevice having a first light extraction surface, a wavelength convertingelement, and a second light extraction surface. A majority of lightextracted from the light emitting device is extracted from the firstlight extraction surface. The first light extraction surface has a firstarea. The second light extraction surface is disposed over the firstlight extraction surface and has a second area. The first area is largerthan the second area.

In some embodiments of the invention, a device includes a plurality oflight emitting devices each having a first light extraction surface. Amajority of light extracted from each of the light emitting devices isextracted from the first light extraction surfaces. A wavelengthconverting element is disposed over at least two of the first lightextraction surfaces. The wavelength converting element has a secondlight extraction surface. The area of the second light extractionsurface is smaller than an area that is the sum of the areas of each ofthe first light extraction surfaces in the plurality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a device including an LED and awavelength converting element, according to some embodiments.

FIG. 2 is a cross sectional view of one example of an LED.

FIG. 3 is a top view of a portion of the device illustrated in FIG. 1,showing the light output surfaces of the LED and the wavelengthconverting element.

FIGS. 4, 5, 6, 7, and 8 are cross sectional views of devices includingLEDs and wavelength converting elements of different shapes, accordingto some embodiments.

FIGS. 9, 10, 11, 12, 13, 14, 15, 16, and 17 illustrate the light outputsurfaces of the LED and wavelength converting elements of differentshapes, according to some embodiments.

FIG. 18 is a cross sectional view of a device including an LED,wavelength converting element, and transparent structure which mayreduce the light output area and thereby increase luminance.

FIG. 19 illustrates the light output surfaces of a line of four LEDs anda shared wavelength converting element.

FIG. 20 illustrates the light output surfaces of a two by four array ofLEDs and a shared wavelength converting element

FIG. 21 illustrates the light output surfaces of an arrangement oftwelve LEDs and a shared wavelength converting element.

FIG. 22 illustrates the light output surfaces of a four by four array ofLEDs and a shared wavelength converting element.

FIG. 23 illustrates the light output surfaces of a line of four LEDs anda shared wavelength converting element, where the wavelength convertingelement is shaped to accommodate bonding structures on the light outputsurfaces of the LEDs.

DETAILED DESCRIPTION

Some lighting applications require sources with high luminance or highilluminance. Luminance is luminous flux per unit area, per solid angle.Luminance is usually expressed in the units [cd/m²] or [lm/sr/m²].Illuminance is the luminous flux per unit area. Illuminance is usuallyexpressed in the units [lm/m²]. Illuminance measures the light emittedfrom an area, while luminance measures light that is not only confinedto a certain area, but also confined to a set of angles. In embodimentsof the invention, the light extraction area of the source is confined,so both luminance and illuminance are changed as compared to anidentical device without a confined light extraction area. Because thestructures described in some embodiments do not usually change theangles of emission, the fractional change to luminance and illuminanceare the same. High luminance allows for greater beam control, or forsmaller and less expensive optics. Some applications where highluminance may be desirable include automotive, flash (for example, asapplied to photography), and directional illumination.

In embodiments of the invention, the luminance in a semiconductor lightemitting device such as an LED may be increased by reducing the area ofthe light emitting surface. The light emitting surface of the structuremay be reduced by disposing a wavelength converting element over theLED. A light emitting surface area of the wavelength converting elementmay be smaller than the light emitting surface area of the LED. At leasta portion of light extracted from the LED may be forced to exit throughthe smaller area of the wavelength converting element, which mayincrease the illuminance and luminance of the structure.

Though in the examples below the semiconductor light emitting devicesare III-nitride LEDs that emit blue or UV light, semiconductor lightemitting devices besides LEDs such as laser diodes and semiconductorlight emitting devices made from other materials systems such as otherIII-V materials, III-phosphide, III-arsenide, II-VI materials, ZnO, orSi-based materials may be used in embodiments of the invention.

FIG. 1 is a cross sectional view of an embodiment of the invention. AnLED 1 is disposed on a support 32. One example of an LED 1 is describedbelow in reference to FIG. 2.

Any suitable support 32 may be used. Examples include, for example, ametal core PC board, an insulating substrate such as a ceramicsubstrate, or a conductive substrate such as a metal substrate. Support32 may provide electrical connections to power LED 1, as is known in theart. LED 1 is attached to support 32 by any suitable structureincluding, for example, conductive interconnects, solder, metalinterconnects, gold-gold interconnects, or conductive glue. (In the caseof a conductive support, electrical isolation to prevent shorting in theLED may be provided on one or more surfaces of the support by one ormore insulating layers, as is known in the art.)

FIG. 2 illustrates a III-nitride LED 1 that may be used in embodimentsof the present invention. Any suitable semiconductor light emittingdevice may be used and embodiments of the invention are not limited tothe device illustrated in FIG. 2. The device of FIG. 2 is formed bygrowing a III-nitride semiconductor structure on a growth substrate 10as is known in the art. The growth substrate is often sapphire but maybe any suitable substrate such as, for example, SiC, Si, GaN, or acomposite substrate. A surface of the growth substrate on which theIll-nitride semiconductor structure is grown may be patterned,roughened, or textured before growth, which may improve light extractionfrom the device. A surface of the growth substrate opposite the growthsurface (i.e. the surface through which a majority of light is extractedin a flip chip configuration) may be patterned, roughened or texturedbefore or after growth, which may improve light extraction from thedevice.

The semiconductor structure includes a light emitting or active regionsandwiched between n- and p-type regions. An n-type region 16 may begrown first and may include multiple layers of different compositionsand dopant concentration including, for example, preparation layers suchas buffer layers or nucleation layers, and/or layers designed tofacilitate removal of the growth substrate, which may be n-type or notintentionally doped, and n- or even p-type device layers designed forparticular optical, material, or electrical properties desirable for thelight emitting region to efficiently emit light. A light emitting oractive region 18 is grown over the n-type region. Examples of suitablelight emitting regions include a single thick or thin light emittinglayer, or a multiple quantum well light emitting region includingmultiple thin or thick light emitting layers separated by barrierlayers. A p-type region 20 may then he grown over the light emittingregion. Like the n-type region, the p-type region may include multiplelayers of different composition, thickness, and dopant concentration,including layers that are not intentionally doped, or n-type layers.

After growth, a p-contact is formed on the surface of the p-type region.The p-contact 21 often includes multiple conductive layers such as areflective metal and a guard metal which may prevent or reduceelectromigration of the reflective metal. The reflective metal is oftensilver but any suitable material or materials may be used. After formingthe p-contact 21, a portion of the p-contact 21, the p-type region 20,and the active region 18 is removed to expose a portion of the n-typeregion 16 on which an n-contact 22 is formed. The n- and p-contacts 22and 21 are electrically isolated from each other by a gap 25 which maybe filled with a dielectric such as an oxide of silicon or any othersuitable material. Multiple n-contact vias may be formed; the n- andp-contacts 22 and 21 are not limited to the arrangement illustrated inFIG. 2. The n- and p-contacts may be redistributed to form bond padswith a dielectric/metal stack as is known in the art.

In order to form electrical connections to the LED 1, one or moreinterconnects 26 and 28 are formed on or electrically connected to then- and p-contacts 22 and 21. Interconnect 26 is electrically connectedto n-contact 22 in FIG. 5. Interconnect 28 is electrically connected top-contact 21 Interconnects 26 and 28 are electrically isolated from then- and p-contacts 22 and 21 and from each other by dielectric layer 24and gap 27. Interconnects 26 and 28 may be, for example, solder, studbumps, gold layers, or any other suitable structure.

The substrate 10 may be thinned or entirely removed. In someembodiments, the surface of substrate 10 exposed by thinning ispatterned, textured, or roughened to improve light extraction.

In some embodiments, a transparent region is disposed between thesemiconductor structure of the LED and the wavelength convertingelement, described below. The transparent region may be an empty cavityor a filled region. The transparent region may behave as a mixing box,which recycles light and may increase the likelihood that the light isextracted from the semiconductor structure of the LED and impinges onthe wavelength converting element. The transparent region may be thegrowth substrate 10 as illustrated in the device of FIG. 2. In someembodiments, the growth substrate is removed or thinned and thetransparent region is a non-growth substrate material, such as a slab ofglass, sapphire, silicone, or any other suitable material. Thesemiconductor structure of the LED is on the order of microns thick, andthe transparent region is on the order of hundred of microns thick. Insome embodiments, the transparent region is at least 20 times and nomore than 100 times thicker than a thickest part of the semiconductorstructure. The transparent region may be omitted in some embodiments, inparticular when a diffuse reflector, and/or the wavelength convertingelement itself may substitute for a mixing box.

Many individual LEDs are formed on a single wafer then diced from awafer of devices. The invention is not limited to the particular LEDillustrated in FIG. 2; any suitable device may be used. The LEDs arerepresented in the following figures by block 1.

Returning to FIG. 1, a wavelength converting element 30 is disposed overthe LED 1. The wavelength converting element includes one or morewavelength converting materials which may be, for example, conventionalphosphors, organic phosphors, quantum dots, organic semiconductors,II-VI or III-V semiconductors, II-VI or III-V semiconductor quantum dotsor nanocrystals, dyes, polymers, or other materials that luminesce. Thewavelength converting material absorbs light emitted by the LED andemits light of one or more different wavelengths. Unconverted lightemitted by the LED is often part of the final spectrum of lightextracted from the structure, though it need not be. The final spectrumof light extracted from the structure may be white or monochromatic.Examples of common combinations include a blue-emitting LED combinedwith a yellow-emitting wavelength converting material, a blue-emittingLED combined with green- and red-emitting wavelength convertingmaterials, a UV-emitting LED combined with blue- and yellow-emittingwavelength converting materials, and a UV-emitting LED combined withblue-, green-, and red-emitting wavelength converting materials.Wavelength converting materials emitting other colors of light may beadded to tailor the spectrum of light extracted from the structure.

In some embodiments, wavelength converting element 30 is a structurethat is fabricated separately from LED 1 and attached to LED 1, forexample through wafer bonding or a suitable adhesive such as silicone orepoxy. One example of such a pre-fabricated wavelength convertingelement is a ceramic phosphor, which is formed by, for example,sintering powder phosphor or the precursor materials of phosphor into aceramic slab, which may then be diced into individual wavelengthconverting elements. A ceramic phosphor may also be formed by, forexample tape casting, where the ceramic is fabricated to the correctshape, with no dicing or cutting necessary. Examples of suitablenon-ceramic pre-formed wavelength converting elements include powderphosphors that are disposed in transparent material such as silicone orglass that is rolled, cast, or otherwise formed into a sheet, thensingulated into individual wavelength converting elements, and phosphormixed with silicone and disposed on a transparent substrate. Thewavelength converting members may have any suitable cross-section, e.g.square, rectangular, polygonal, hexagonal, circular. The threedimensional shape may include a polyhedron, uniform polyhedral, Johnsonsolid, prism, anti-prism or any other suitable shape.

A reflective material 34 is disposed on the sides of LED 1 andwavelength converting element 30. The reflective material 34 may be, forexample, a diffuse reflector, such as reflective particles such as TiOxdisposed in a transparent material such as silicone, a materialreflector such as one or more layers of silver, aluminum, gold, or anyother reflective material, a distributed Bragg reflector, or any othersuitable structure. Reflective material 34 may be formed by moldingand/or pressing over the LED 1 and wavelength converting element 30, orany other suitable technique. Reflective material 34 may be flush withthe top surface 35 of wavelength converting element 30 as illustrated inFIG. 1, though this is not required.

Due to the presence of reflective material 34 along the sidewalls of LED1 and wavelength converting element 30, a majority of light extractedfrom LED 1 exits through the top surface 37 of LED 1. A majority oflight extracted from wavelength converting element 30 exits through thetop surface 35 of wavelength converting element 30. An area 31 of thelight extraction surface 35 of wavelength converting element 30 issmaller than an area 33 of the light extraction surface 37 of LED 1, asillustrated in FIG. 3, which is a top view of a portion of the device ofFIG. 1.

The light output surface area 31 of the wavelength converting element 30may be no more than 90% of the light output surface area 33 of LED 1 insome embodiments, no more than 80% in some embodiments, no more than 60%in some embodiments, at least 30% in some embodiments, and at least 50%in some embodiments.

The structure illustrated in FIG. 1 may be formed as follows. LED 1 isformed, as described above in reference to FIG. 2. A wafer of LEDs maybe diced into individual or groups of devices. Wavelength convertingelement 30 is formed. A wafer of wavelength converting elements may bediced into individual wavelength converting elements which correspond toa single LED, or a larger wavelength converting element whichcorresponds to more than one LED, as described below. LED 1 is attachedto support 32, for example by soldering or any other suitable technique.Multiple LEDs may be attached to a wafer of supports 32. Before or afterattaching LED 1 to support 32, wavelength converting element 30 may beattached to LED 1, for example by gluing or any other suitabletechnique. Reflective material 34 is disposed around LED 1 andwavelength converting element 30, for example by molding, pressing, orby any other suitable technique. Excess reflective material, such as,for example, reflective material disposed over the top surface 35 ofwavelength converting element 30 after forming the reflective material,may be removed, for example by wet or dry bead blasting, mechanicaltechniques, or any other suitable technique.

In some embodiments, wavelength converting element 30 is not apre-formed structure that is attached to LED 1, rather wavelengthconverting element 30 is formed on LED L For example, a layer ofreflective material 34 may be disposed over an LED 1 on a support 32. Anopening in reflective material 34 may be formed, corresponding to theshape of wavelength converting element 30. A wavelength convertingmaterial mixed with a transparent material such as silicone may then beinjected or otherwise disposed in the opening, then cured if necessaryto form wavelength converting element 30.

The wavelength converting element may have any suitable shape. Thewavelength converting element 30 illustrated in FIGS. 1 and 3 issubstantially square with substantially vertical sidewalls, and iscentered on the LED 1. This is not necessary, as illustrated in FIGS. 4,5, 6, 7, and 8, which are cross sectional views of alternativeembodiments, and FIGS. 9, 10, 11, 12, 13, 14, 15, 16, and 17, which aretop views of the light output surfaces of the LED and wavelengthconverting element in alternative embodiments. The cross sectional viewsillustrated in FIGS. 1, 4, 5, 6, 7, and 8 may have any of the shapesillustrated in the top views of FIGS. 3, 9, 10, 11, 12, 13, 14, 15, 16,and 17. Similarly, the top views illustrated in FIGS. 3, 9, 10, 11, 12,13, 14, 15, 16, and 17 may have any of the cross sections illustrated inFIGS. 1, 4, 5, 6, 7, and 8.

In the device of FIG. 4, the sidewall(s) 41 of wavelength convertingelement 30 are sloped. The top, light extraction surface 35 of thewavelength converting element 30 is smaller than the bottom surface 40,which is the surface closest to LED 1. Accordingly, sidewall(s) 41 forman acute angle with bottom surface 40. All, a portion, or only one ofthe sidewall(s) of the wavelength converting element 30 may be angled asillustrated in FIG. 4. The bottom surface 40 of wavelength convertingelement 30 may be the same size as the light output surface 37 of LED 1,as illustrated in FIG. 4, though this is not required. In particular,the bottom surface 40 of wavelength converting element 30 may be smallerthan the light output surface 37 of LED 1.

The cross section of the wavelength converting element 30 of the deviceof FIG. 5 is similar to that of FIG. 4, in that one or more of thesidewall(s) is angled and forms an acute angle with bottom surface 40such that the light extraction surface 35 is smaller than the bottomsurface 40. In the device of FIG. 5, the bottom surface 40 of wavelengthconverting element 30 is larger than the light output surface 37 of LED1. Since the light extraction surface 35 of wavelength convertingelement 30 is smaller than the light output surface 37 of LED 1, thedevice may still exhibit increased luminance, as compared to a devicewhere the areas of the light output surfaces of the LED and thewavelength converting element are the same.

In the device of FIG. 6, the sidewall(s) 41 of wavelength convertingelement 30 are sloped opposite the device illustrated in FIGS. 4 and 5.In particular, the top, light extraction surface 35 of the wavelengthconverting element 30 is larger than the bottom surface 40, which is thesurface closest to LED 1. Accordingly, sidewall(s) 41 form an acuteangle with light extraction surface 35. All, a portion, or only one ofthe sidewall(s) of the wavelength converting element 30 may be angled asillustrated in FIG. 6. Both the bottom surface 40 and the top, lightextraction surface 35 of wavelength converting element 30 are smallerthan the light output surface 37 of LED 1.

In the devices of FIGS. 7 and 8, the sidewall(s) of the wavelengthconverting element 30 are divided into more than one section, where thedifferent sections have different profiles. In the device of FIG. 7, abottom portion 44 of the wavelength converting element 30 is wider thena top portion 43 of the wavelength converting element 30. Both portions43 and 44 of side-wall(s) 41 are substantially vertical in theembodiment illustrated in FIG. 7. The area of the top, light extractionsurface 35 is greater than the area of the bottom surface 40 ofwavelength converting element 30.

In the device of FIG. 8, a bottom portion 45 of the wavelengthconverting element has sloped sidewall(s), and a top portion 43 of thewavelength converting element 30 has substantially vertical sidewall(s).The area of the top, light extraction surface 35 is greater than thearea of the bottom surface 40 of wavelength converting element 30.

FIGS. 9, 10, 11, 12, 13, 14, 15, 16, and 17 are views of differentembodiments, illustrating the size, shape, and placement of the lightextraction surface 35 of wavelength converting element 30 relative tothe light extraction surface 37 of LED 1, when viewed from the top ofthe device. In each of FIGS. 9, 10, 11, 12, 13, 14, 15, 16, and 17, thearea of the light extraction surface 35 of wavelength converting element30 is smaller than the area of the light extraction surface 37 of LED 1.In an actual device according to FIGS. 9, 10, 11, 12, 13, 14, 15, 16,and 17, the portions of the LEDs visible in the figures would be coveredby reflective material 34, as illustrated in the cross sections of FIGS.1, 4, 5, 6, 7, and 8.

In FIG. 9, the top surface 35 of the wavelength converting element isrectangular and is centered on the light extraction surface 37 of LED 1.In this example and the examples of FIGS. 9, 10, 13, 14, 15, 16, and 17,the wavelength converting element 30 has four sidewalls.

In FIG. 10, the top surface 35 of the wavelength converting element isrectangular. It is centered on light extraction surface 37 of LED 1, butoverhangs the sides of the light extraction surface 37 of LED 1 inregions 46.

In FIG. 11, the top surface 35 of the wavelength converting element iscircular. The wavelength converting element is centered on the lightextraction surface 37 of LED 1. In this example the wavelengthconverting element 30 has a single sidewall.

In FIG. 12, the top surface 35 of the wavelength converting element iscircular. A circular hole 47 is formed in the center of the wavelengthconverting element and extends through the entire thickness of thewavelength converting element, exposing the light extraction surface 37of LED 1. The wavelength converting element is centered on the lightextraction surface 37 of LED 1.

The embodiment illustrated in FIG. 12 is not limited to a circularwavelength converting element with a circular hole 47. Both thewavelength converting element and the hole may be any suitable shape andneed not be the same shape. The hole need not be centered in thewavelength converting element as illustrated, and the wavelengthconverting element need not be centered on the LED as illustrated. Inthis example the wavelength converting element 30 has a single outersidewall 41 and a second inner sidewall 410. The angle of the inner andouter sidewalls may be the same or different. For this example, FIGS. 1,4, 5, 6, 7 and 8 illustrate the shape of the outer sidewall 41 and donot show the inner sidewall 410.

In FIG. 13, the top surface 35 of the wavelength converting element issquare, but the wavelength converting element is positioned in a cornerof the light extraction surface 37 of LED 1, rather than centered overthe light extraction surface 37. Two of the edges of the top surface 35of the wavelength converting element align with two of the edges of thelight extraction surface 37, though strict alignment is not required.

In FIG. 14, the top surface 35 of the wavelength converting element isrectangular, but the wavelength converting element is positioned offcenter. One or more edges of the wavelength converting element arealigned with an edge of the light extraction surface 37 of LED 1, ratherthan centered over the light extraction surface 37, though strictalignment is not required.

In FIG. 15, the top surface 35 of the wavelength converting element istrapezoidal. Although the figure shows the cross section of an isoscelestrapezoid, other trapezoids are contemplated and are included within thescope of the invention.

In FIG. 16, the top surface 35 of the wavelength converting element issquare and centered over the light extraction surface 37, but with theedges of the wavelength converting element oriented at 45 degreesrelative to the edges of the light extraction surface, rather thanparallel, such that the wavelength converting element appears as adiamond. Other orientations of the square or of any cross section shapeare also contemplated and are included within the scope of theinvention.

In FIG. 17, the top surface 35 of the wavelength converting element is aparallelogram.

Other cross sections and top views are possible. The shape of thewavelength converting element 30 is not limited to the examplesillustrated.

In some embodiments, the area of the surface from which light isextracted from the device is made smaller than the area of the surfacefrom which light is extracted from the LED by disposing an additionaloptical element disposed over the wavelength converting element, ratherthan by the wavelength converting element itself. Such a device isillustrated in FIG. 18. An LED 1 is attached to a support 32 and awavelength converting element 30 is attached to the LED as describedabove. The wavelength converting element 30 is the same size as LED 1 inthe embodiment illustrated, though this is not required. A transparentstructure 48 is disposed over wavelength converting element 30.Reflective material 34 is disposed on the sides of the transparentstructure 48, the wavelength converting element 30, and the LED 1. Thetransparent structure 48 may be, for example, glass, sapphire, silicone,epoxy, GaN, SiC plastic, or any other suitable transparent material. Itis formed on or attached to wavelength converting element 30 by anysuitable technique including, for example, gluing with a siliconeadhesive, before forming reflective material 34, as described above. Thearea 49 of the top, light extraction surface of the transparentstructure 48 is smaller than the light extraction surface 35 of thewavelength converting element 30 and the light extraction surface 37 ofLED 1, which may increase the luminance of the structure.

FIGS. 19, 20, 21, 22, and 23 are top views illustrating embodimentswhere a single wavelength converting element is disposed over multipleLEDs 1 a, 1 b, 1 e, and 1 d. In each case, the area of the lightextraction surface 35 of the wavelength converting element 30 is smallerthan the combined area of the light extraction surfaces 37 of the LEDs 1a-d, and the area between the LEDs 1 a-d. The light ex traction surface35 area of the wavelength converting element 30 may be no more than 90%of the combination of the sum of the areas of the light output surfacesof the LEDs 1 a-d and the area between the LEDs 1 a-d in some,embodiments, no more than 80% in some embodiments, no more than 60% insome embodiments, at least 30% in some embodiments, and at least 50% insome embodiments.

In embodiments with a wavelength converting element disposed overmultiple LEDs, the shape of the light emitting area can be changedarbitrarily by changing the arrangement of the LEDs. In effect, in theembodiments of FIGS. 19, 20, 21, 22, and 23, a group of LEDs substitutesfor the single LEDs illustrated in FIGS. 1 and 3-18. In particular, thedevices illustrated in FIGS. 1 and 3-18 may be made by placing awavelength convening element over a single 1 mm² die, or over four 0.25mm² dies. Using multiple LEDs instead of a single LED gives freedom interms of optical shape, drive current/voltage, reuse of a single die fordifferent size parts (for manufacturing simplicity) and allows forindividual addressability of the LEDs (turn on one part of the structureat a time).

FIGS. 19, 20, 21, 22, and 23 illustrate the relative arrangement of theLEDs and the wavelength converting element. In an actual deviceaccording to FIGS. 19, 20, 21, 22, and 23, the portions of the LEDsvisible in the figures would be covered by reflective material 34, asillustrated in the cross sections of FIGS. 1, 4, 5, 6, 7, and 8. In theembodiments illustrated in FIGS. 19, 20, 21, 22, and 23, the wavelengthconverting element covers at least a portion of all of the LEDs in thegroup. More or fewer LEDs may be used in any of the embodimentsillustrated.

In FIG. 19, a wavelength converting element 30 with a rectangular topsurface 35 is disposed over a line of four LEDs 1 a, 1 b, 1 c, and 1 d.The top surface 35 of wavelength converting element 30 is narrower thanthe LEDs, such that portions of each of the LEDs 1 a, 1 b, 1 e, and 1 dare not covered by the wavelength converting element. As illustrated inFIG. 19, the sides of the wavelength converting element 30 extend beyondthe edges of LEDs 1 a and 1 d. This is not required: in someembodiments, the wavelength converting element does not extend beyondthe edges of the LEDs in any dimension.

In FIG. 20, a wavelength converting element 30 with a rectangular topsurface 35 is disposed over a 2×4 array of eight LEDs 1 a, 1 b, 1 c, 1d, 1 e, 1 f, 1 g, and 1 h. The top surface 35 of wavelength convertingelement 30 is narrower than the array of LEDs, such that portions ofeach of the LEDs 1 a, 1 b, 1 e, 1 d, 1 e, 1 f, 1 g, and 1 h are notcovered by the wavelength converting element 30.

In FIG. 21, a wavelength converting element 30 with a circular topsurface 35 is disposed over an array of 12 LEDs 1 a, 1 b, 1 c, 1 d, 1 e,1 f, 1 g, 1 h, 1 i, 1 j, 1 k, and 1 l arranged like a plus sign. Themiddle four LEDs 1 d, 1 e, 1 h, and 1 i are completely covered bywavelength converting element 30. Portions of LEDs 1 a, 1 b, 1 c, 1 g, 1j, 1 k, and 1 l are not covered by the wavelength converting element 30.The embodiment illustrated in FIG. 21 is a square array of LEDs coveredby a round wavelength converting element. LEDs in the array that are notcovered by the round wavelength converting element are removed,resulting in the plus-sign shaped array illustrated. The embodimentillustrated may be extended to any device where the wavelengthconverting element is a shape that does not readily correspond to arectangular array of rectangular LEDs.

In FIG. 22, a wavelength converting element 30 with a rectangular topsurface 35 is disposed over a 4×4 array of 16 LEDs 1 a, 1 b, 1 e, 1 d, 1e, 1 f, 1 g, 1 h, 1 i, 1 j, 1 k, 1 l, 1 m, 1 n, 1 o, and 1 p. The topsurface 35 of wavelength converting element 30 is smaller than the arrayof LEDs, such that portions of the LEDs on the outside of the array,LEDs 1 a, 1 b, 1 c, 1 d, 1 e, 1 h, 1 i, 1 l, 1 m, 1 n, 1 o, and 1 p arenot covered by the wavelength converting element 30. The LEDs in thecenter of the array, LEDs 1 f, 1 g, 1 j, and 1 k are completely coveredby the wavelength converting element.

FIG. 23 illustrates a wavelength converting element 30 with asubstantially rectangular top, light extraction surface 35 disposed overa line of four LEDs 1 a, 1 b, 1 c, and 1 d. One edge 52 of the lightextraction surface 35 has regions 54 that are shaped to accommodatebonding structures 50 formed on the light extraction surfaces 37 of eachof the LEDs 1 a, 1 b, 1 e, and 1 d. Though the bonding structures 50illustrated are wire bonds, they may be any suitable bonding structure.Any of the wavelength converting elements described above may be shapedsuch that they do not cover or otherwise interfere with a bondingstructure or any other structure formed the light extraction surface ofthe LED, as illustrated in FIG. 23. The wavelength converting elementillustrated may be readily formed by tapecasting, in which the regions54 may be easily formed, or by any other suitable method.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. Therefore, it is not intended that the scopeof the invention be limited to the specific embodiments illustrated anddescribed.

What is claimed is:
 1. A device comprising: a light emitting devicehaving a first light extraction surface extending from one sidewall ofthe light emitting device to another sidewall of the light emittingdevice, the first light extraction surface having a first area, and amajority of light extracted from the light emitting device is extractedfrom the first light extraction surface, and a wavelength convertingelement disposed over the first light extraction surface and having abottom surface at least partially contacting the first light extractionsurface, the wavelength converting element having a second lightextraction surface opposite the bottom surface and disposed over thefirst light extraction surface, the second light extraction surfacehaving a second area smaller than the first area of the first lightextraction surface, and the bottom surface having a third area that isequal to the first area of the first light extraction surface and havinga width equal to a maximum width of the wavelength converting element.2. The device of claim 1, further comprising a reflective materialdisposed along sidewalls of the wavelength converting element, whereinthe second light extraction surface is level with a surface of thereflective material.
 3. The device of claim 1, wherein the second areaof the second light extraction surface is 30% to 60% of the first area.4. The device of claim 1, wherein the second light extraction surfacehas a shape of a circle.
 5. The device of claim 4, wherein a hole isformed in a center of the second light extraction surface that extendsthrough an entire thickness of the wavelength converting element andexposes the first light extraction surface.
 6. The device of claim 1,wherein the second light extraction surface has a shape of aparallelogram.
 7. The device of claim 5, wherein the parallelogram is asquare or a trapezoid.
 8. The device of claim 1, wherein the secondlight extraction surface extends past at least one side of the firstlight extraction surface.
 9. The device of claim 1, wherein a center ofthe second light extraction surface is not aligned with a center of thefirst light extraction surface.
 10. The device of claim 1, wherein afirst edge of the second light extraction surface aligns with a firstedge of the first light extraction surface.
 11. The device of claim 10,wherein a second edge of the second light extraction surface aligns witha second edge of the second light extraction surface.
 12. The device ofclaim 1, wherein the wavelength converting element has a top portioncomprising the second light extraction surface and a bottom portioncomprising the bottom surface, the top portion comprising firstsidewalls that are perpendicular to the second light extraction surfaceand the bottom portion comprising second sidewalls that are angled withrespect to the first sidewalls.
 13. The device of claim 1, furthercomprising a transparent structure disposed over the second lightextraction surface.
 14. The device of claim 1, wherein the wavelengthconverting element has angled sidewalls extending in a straight linefrom the bottom surface to the second light extraction surface.
 15. Thedevice of claim 2, wherein the reflective material comprises particlesof TiO_(x) disposed in a silicone.
 16. The device of claim 2, whereinthe reflective material is at least one of silver, aluminum, gold, and adistributed Bragg reflector.
 17. A device comprising: a light emittingdevice having a first light extraction surface extending from onesidewall of the light emitting device to another sidewall of the lightemitting device, the first light extraction surface having a first area,and a majority of light extracted from the light emitting device isextracted from the first light extraction surface, and a wavelengthconverting element disposed over the first light extraction surface andhaving a bottom surface at least partially contacting the first lightextraction surface and a second light extraction surface opposite thebottom surface and disposed over the first light extraction surface, thesecond light extraction surface having a second area smaller than thefirst area of the first light extraction surface, the bottom surfacehaving a third area that is less than the first area of the first lightextraction surface, and the wavelength converting element having asmaller maximum width parallel to the bottom surface than a maximumwidth of the light emitting device parallel to the bottom surface andhaving sidewalls that are perpendicular to the bottom surface.
 18. Thedevice of claim 17, wherein the second area of the second lightextraction surface is a same size as the third area of the bottomsurface.
 19. A device comprising: a light emitting device having a firstlight extraction surface extending from one sidewall of the lightemitting device to another sidewall of the light emitting device, thefirst light extraction surface having a first area, and a majority oflight extracted from the light emitting device is extracted from thefirst light extraction surface, and a wavelength converting elementdisposed over the first light extraction surface and having a bottomsurface at least partially contacting the first light extraction surfaceand a second light extraction surface opposite the bottom surface anddisposed over the first light extraction surface, the second lightextraction surface having a second area smaller than the first area ofthe first light extraction surface, the bottom surface having a thirdarea that is less than the first area of the first light extractionsurface, the wavelength converting element having a top portioncomprising the second light extraction surface and a bottom portioncomprising the bottom surface, the top portion comprising firstsidewalls that are perpendicular to the second light extraction surfaceand the bottom portion comprising second sidewalls that areperpendicular to the bottom surface, and the top portion having asmaller maximum width parallel to the bottom surface than a maximumwidth of the bottom portion parallel to the bottom surface.